Quasi-two-dimensional electron gas at the interface of γ-Al2O3/SrTiO3 heterostructures grown by atomic layer deposition
Abstract
We report the formation of a quasi-two-dimensional electron gas (2-DEG) at the interface of γ-Al2O3/TiO2-terminated SrTiO3 (STO) grown by atomic layer deposition (ALD). The ALD growth of Al2O3 on STO(001) single crystal substrates was performed at temperatures in the range of 200–345 °C. Trimethylaluminum and water were used as co-reactants. In situ reflection high energy electron diffraction, ex situ x-ray diffraction, and ex situ cross-sectional transmission electron microscopy were used to determine the crystallinity of the Al2O3 films. As-deposited Al2O3 films grown above 300 °C were crystalline with the γ-Al2O3 phase. In situ x-ray photoelectron spectroscopy was used to characterize the Al2O3/STO interface, indicating that a Ti3+ feature in the Ti 2p spectrum of STO was formed after 2–3 ALD cycles of Al2O3 at 345 °C and even after the exposure to trimethylaluminum alone at 300 and 345 °C. The interface quasi-2-DEG is metallic and exhibits mobility values of ∼4 and 3000 cm2 V−1 s−1 at room temperature and 15 K, respectively. The interfacial conductivity depended on the thickness of the Al2O3 layer. The Ti3+ signal originated from the near-interfacial region and vanished after annealing in an oxygen environment.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Sep 15, 2015
- Source ID
- 10.1063/1.4930575
Entities
People
- Agham Posadas
- Alexander A Demkov
- David J Smith
- Jean Jordan-sweet
- John G Ekerdt
- Kristy J Kormondy
- Martin D. Mcdaniel
- Nicholas J. Goble
- Sirong Lu
- Thong Q. Ngo
- Xuan P. A. Gao
Organizations
- Air Force Office of Scientific Research
- Arizona State University
- Case Western Reserve University
- International Business Machines Corporation (Armonk, NY)
- Office of Naval Research
- University of Texas at Austin